1. Field
The presently disclosed subject matter relates to semiconductor light-emitting devices in which light emitted from a semiconductor light-emitting chip is wavelength-converted by a wavelength converting layer, and to manufacturing methods for the same. More particularly, the disclosed subject matter relates to semiconductor light-emitting devices for a vehicle light and the like, which can emit light having a high light-emitting efficiency from a small light-emitting surface via a thin wavelength converting layer including a high density of phosphor, and to methods of manufacturing such devices, which can emit a wavelength-converted light having a similar chromaticity even between different manufacturing lots.
2. Description of the Related Art
Semiconductor light-emitting devices, in which a part of the light emitted from a semiconductor light-emitting chip is converted into light having a different wavelength by a phosphor and in which a mixture light comprising the light having the different wavelength mixed with the light emitted directly from the light-emitting chip is emitted, have been used as a light source for various lighting units. Forming a wavelength converting layer for the semiconductor light-emitting devices has been achieved by use of various methods such as applying a transparent resin including a phosphor on a top surface of the semiconductor light-emitting chip, printing a transparent resin on the top surface of the light-emitting chip, and dispensing a transparent resin in a cavity for mounting a light-emitting chip.
A first conventional semiconductor light-emitting device including a wavelength-converting layer in a cavity, for example, is disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2006-48934). FIG. 9 is a side cross-section view showing the first conventional semiconductor light-emitting device including the wavelength converting layer disposed in the cavity for mounting a plurality of semiconductor light-emitting chips therein, which is disclosed in Patent Document No. 1.
The conventional semiconductor light-emitting device 20 includes: a casing 23 having a cavity 23a that includes a substantially rectangular opening and a bottom surface; conductor patterns 25 formed on the bottom surface of the cavity 23a and extending to the outside of the casing 23 for receiving a power supply; a plurality of semiconductor light-emitting chips 22 having a top and bottom electrode mounted on the conductor patterns 25, each of the top and bottom electrodes of the semiconductor light-emitting chips 22 connected to the corresponding portion of the conductor patterns 25 via a bonding wire 27 or directly; and a wavelength converting layer 26 including a phosphor 26a disposed in the cavity 23a of the casing 23 so as to encapsulate the semiconductor light-emitting chips 22 in the cavity 23a. 
A second conventional semiconductor light-emitting device including a dome-shaped wavelength-converting layer, for example, is disclosed in Patent Document No. 2 (Japanese Patent Application Laid Open JP2009-135136). FIG. 10 is a side cross-section view showing the second conventional semiconductor light-emitting device in which a dome-shaped wavelength converting layer is disposed on a top surface of a semiconductor light-emitting chip, and which is disclosed in Patent Document No. 2.
The second conventional semiconductor light-emitting device 30 includes: a mounting board 37; a semiconductor light-emitting chip 31 including a chip substrate 32 and a semiconductor epitaxial layer 33 grown on the chip substrate 32, and the semiconductor light-emitting chip 31 mounted on the mounting board 37; and a dome-shaped wavelength converting layer 36 including a phosphor 36a disposed on a top surface of the semiconductor light-emitting chip 31 so as to be able to wavelength-convert light emitted from the semiconductor epitaxial layer 31. In this case, the conventional device 30 can also include a plurality of semiconductor light-emitting chips 31 mounted along with the dome-shaped wavelength converting layer 36 on the mounting board 37.
A third conventional semiconductor light-emitting device including a wavelength-converting layer formed by a printing method, for example, is disclosed in Patent Document No. 3 (Japanese Patent Application Laid Open JP2010-118531). FIG. 11 is a perspective view showing the third conventional semiconductor light-emitting device disclosed in Patent Document No. 3. The third conventional semiconductor light-emitting device 40 includes: a mounting board 47; a plurality of semiconductor light-emitting chips 42 mounted on the mounting board 47; and a wavelength converting layer 46 formed on the mounting board 47 by a printing method so as to cover the plurality of semiconductor light-emitting chips 42.
Each of the above-described conventional semiconductor light-emitting devices can include a plurality of semiconductor light-emitting chips and can emit light having a substantially white color tone and a high light intensity via the wavelength converting layer. Accordingly, the conventional semiconductor light-emitting devices can be used as a light source for a vehicle headlight as well as other vehicle and non-vehicle applications in which high quality white light is desired. In addition, inventors of the presently disclosed subject matter disclose a semiconductor light-emitting device for a vehicle headlight in Patent Document No. 4 (U.S. patent application Ser. No. 13/162,151), which can emit light having a high light-emitting efficiency from a small light-emitting surface via a wavelength converting layer such as a ceramic phosphor plate.
When a semiconductor light-emitting device is used as a light source for a lighting unit such as a vehicle headlight, which controls light emitted from the light-emitting device using a reflector and/or a projector lens, a light-emitting device having a small light-emitting surface may be desired to efficiently control light emitted from the light-emitting device with a small optical structure. The semiconductor light-emitting device disclosed in Patent Document No. 4 can emit light having a high light-emitting efficiency from a small light-emitting surface, and therefore can be a match for the above-described usage.
In the conventional light-emitting devices including the respective wavelength converting layers, an amount of wavelength-converted light may vary in accordance with a respective amount of phosphors included in the wavelength converting layers. Therefore, a thickness of each of the wavelength converting layers is determined in accordance with each density of the phosphors included in the wavelength converting layers in order for the light-emitting devices to emit light having a desirable color tone, and each of the wavelength converting layers needs to be formed so as to become the determined thickness.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: Japanese Patent Application Laid Open JP2006-48934    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2009-135136    3. Patent Document No. 3: Japanese Patent Application Laid Open JP2010-118531    4. Patent Document No. 4: U.S. patent application Ser. No. 13/162,151
In recent years, it has be known that wavelength converting efficiency can be extremely improved by using a wavelength converting layer having a higher density (e.g. more than 50%) than a conventional density with respect to a phosphor contained in the wavelength converting layer, and therefore it has been verified that light-emitting efficiency of a semiconductor device using the wavelength converting layer including a high density of phosphor can improve. However, when light having a desirable color tone is emitted using the wavelength converting layer including a high density of phosphor, the wavelength converting layer can be formed in a thin and uniform thickness so as not to emit light having color variability.
When the wavelength converting layer is formed by the above-described methods, a variation of the thickness may occur in approximately 15 percent of product. The variation of the thickness may rarely cause a problem in which light having a color variability is emitted when the semiconductor light-emitting devices using a relatively thick wavelength converting layer including a low density of phosphor such as the conventional wavelength converting layer are employed as a light source for a general lighting field. However, when a very wide range area is illumined from a small light-emitting surface of a semiconductor device via an optical member such as a reflector, a projector lens and the like, for example as a light source for a vehicle headlight, and especially if the semiconductor device must emit light having a high light-emitting efficiency by using the wavelength converting layer including the phosphor having a high density, the variation of the thickness may become a more serious consideration in order to manufacture a high quality vehicle headlight.
The disclosed subject matter has been devised to consider the above and other problems, features, and characteristics. Thus, embodiments of the disclosed subject matter can include semiconductor light-emitting devices that can emit a wavelength-converted light having a high light-emitting efficiency from a small light-emitting surface by using a thin and uniform wavelength converting layer including a phosphor having a high density, and associated manufacturing methods that do not cause and/or are designed to prevent some of the above-described problems, concerns, and characteristics related to a wavelength converting layer. The disclosed subject matter can also include a semiconductor light-emitting device using a plurality of semiconductor light-emitting chips that can be used for wavelength-converting light having a high light-emitting efficiency via a thin and uniform wavelength converting layer including a high density of phosphor.